Ink jet printers are well known in the printing industry. Ink jet printers are just one of many different types of printing systems that have been developed which include laser electrophotographic printers; LED electrophotographic printers; dot matrix impact printers; thermal paper printers; film recorders; thermal wax printers; dye diffusion thermal transfer printers. Ink jet printing has become recognized as a prominent contender in the digitally controlled, electronic printing arena because, e.g., of its non-impact, low-noise characteristics, its use of plain paper and its avoidance of toner transfers and fixing. However, there is an ongoing demand for improved digitally controlled printing systems that are able to produce high color images at a high speed and low cost using standard paper.
One such improvement is disclosed in copending U.S. patent application Ser. No. 08/954,317 entitled "Continuous Ink Jet Printer With Asymmetric Heating Drop Deflection" by Chwalek, et al., filed Oct. 17, 1997, the disclosure of which is hereby incorporated by reference. That application teaches an apparatus for controlling ink in a continuous ink jet printer that includes an ink delivery channel; a source of pressurized ink communicating with the ink delivery channel; a nozzle bore which opens into the ink delivery channel to establish a continuous flow of ink in a stream, the nozzle bore defining a nozzle bore perimeter; and a droplet generator which causes the stream to break up into a plurality of droplets at a position spaced from the ink stream generator. The droplet generator includes a heater having a selectively-actuated section associated with only a portion of the nozzle bore perimeter, whereby actuation of the heater section produces an asymmetric application of heat to the stream to control the direction of the stream between a print direction and a non-print direction. However, there is no disclosure of any specific inks in this application and the only specific fluid used in the example is water.
Another feature of that patent application is a process for controlling ink in a continuous ink jet printer that includes establishing a continuous flow of ink in a stream which breaks up into a plurality of droplets at a position spaced from the ink stream generator; and asymmetrically applying heat to the stream before the position whereat the stream breaks up into droplets to thereby control the angle at which the ink deflects.
Along with the development of ink jet printing systems, such as the system employing asymmetric heating drop deflection, is the requirement of inks useful in ink jet printing. An ink composition must be capable of meeting very stringent criteria to be useful in ink jet printing. Such properties of major concern of the ink composition are viscosity, surface tension, pH, density, conductivity, adhesive characteristics, wetting characteristics, drying rate and shelf life.
It is an object of this invention to provide an ink jet printing process employing a particular ink useful in a thermally-steered, continuous ink jet print head which provides a greater difference in deflection angle at which the ink deflects.